1. Technical Field
The present invention relates to a physical quantity sensor such as, for example, an MEMS (Micro Electro Mechanical System) sensor, and an electronic apparatus.
2. Related Art
In recent years, a technique which implements a highly sensitive physical quantity sensor having a small size by using an MEMS (Micro Electro Mechanical System) technique has attracted attention.
For example, JP-A-2009-109494 discloses a pendulous capacitive accelerometer. The pendulous capacitive accelerometer disclosed in JP-A-2009-109494 includes a substrate, a sensing plate, a central anchor portion which supports the sensing plate on the substrate, an electrode provided on the sensing plate, and an electrode provided on the substrate. The sensing plate includes a solid proof mass (inertial mass) on the left side of the central anchor portion and a hollow proof mass. When a torque is applied to the respective proof masses due to the acceleration, then the sensing plate performs a seesaw operation about the central anchor portion (hinge axis). The capacitance value of a capacitor varies in response to the seesaw operation of the sensing plate, and a differential capacitive output signal is output from the pendulous capacitive accelerometer.
In addition, JP-A-9-189716 discloses an acceleration sensor in which a rocking body supported by rotational axis lines which are asymmetrically arranged is formed on a silicon substrate, the capacitance is differentially detected using the fact that the rocking body is tilted to one side when being applied with acceleration in the Z direction (seesaw rocking), and the acceleration in the Z direction is detected.
In the pendulous capacitive accelerometer disclosed in JP-A-2009-109494, forming a package for protecting the accelerometer is not taken into account.
In addition, in the acceleration sensor in JP-A-9-189716, even in a case where acceleration in the X direction or the Y direction other than the Z direction occurs, the rocking occurs in the rocking body, and thus acceleration in the Z direction seemingly varies. As such, having detection sensitivity for directions different from the detection direction reduces the detection accuracy of the physical quantity sensor, which becomes a problem.